/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.library.dmatch;

import org.apache.iotdb.library.dmatch.util.CrossCorrelation;
import org.apache.iotdb.library.util.Util;
import org.apache.iotdb.udf.api.UDTF;
import org.apache.iotdb.udf.api.access.Row;
import org.apache.iotdb.udf.api.collector.PointCollector;
import org.apache.iotdb.udf.api.customizer.config.UDTFConfigurations;
import org.apache.iotdb.udf.api.customizer.parameter.UDFParameterValidator;
import org.apache.iotdb.udf.api.customizer.parameter.UDFParameters;
import org.apache.iotdb.udf.api.customizer.strategy.RowByRowAccessStrategy;
import org.apache.iotdb.udf.api.type.Type;

import java.util.ArrayList;

/**
 * This function calculates cross correlation between two input series.
 */
public class UDTFXCorr implements UDTF {

    private final ArrayList<Double> valueArrayList0 = new ArrayList<>();
    private final ArrayList<Double> valueArrayList1 = new ArrayList<>();

    @Override
    public void beforeStart(UDFParameters udfParameters, UDTFConfigurations udtfConfigurations)
            throws Exception {
        udtfConfigurations
                .setAccessStrategy(new RowByRowAccessStrategy())
                .setOutputDataType(Type.DOUBLE);
        valueArrayList0.clear();
        valueArrayList1.clear();
    }

    @Override
    public void transform(Row row, PointCollector collector) throws Exception {
        if (row.isNull(0) || row.isNull(1)) {
            valueArrayList0.add(Double.NaN);
            valueArrayList1.add(Double.NaN);
        } else {
            valueArrayList0.add(Util.getValueAsDouble(row, 0));
            valueArrayList1.add(Util.getValueAsDouble(row, 1));
        }
    }

    @Override
    public void terminate(PointCollector collector) throws Exception {
        ArrayList<Double> correlationArrayList =
                CrossCorrelation.calculateCrossCorrelation(valueArrayList0, valueArrayList1);
        for (int i = 0; i < correlationArrayList.size(); i++) {
            collector.putDouble(i, correlationArrayList.get(i));
        }
    }

    @Override
    public void validate(UDFParameterValidator validator) throws Exception {
        validator
                .validateInputSeriesNumber(2)
                .validateInputSeriesDataType(0, Type.INT32, Type.INT64, Type.FLOAT, Type.DOUBLE)
                .validateInputSeriesDataType(1, Type.INT32, Type.INT64, Type.FLOAT, Type.DOUBLE);
    }

    @Override
    public void beforeDestroy() {
        valueArrayList0.clear();
        valueArrayList1.clear();
    }
}
